Compaction spared a pending tool round's text results but not its
images. The image-retirement pass kept only the newest three image
results across the transcript, so four parallel vision calls in one
unread round lost the oldest image before the model saw any of them.
On a single-prompt run the final media pass lost three of the four:
compaction re-appends the task as a user row after the round, and the
pending round was looked up after that row was added, so nothing was
spared.
Both image passes now skip a pending round that fits the hard share,
and the pending round is found before the task row is re-appended.
Completed rounds and a pending round over the hard share keep the
existing policy.
(cherry picked from commit eb7661f4365f009d5f9ef85e26f2f4b6ac83632e)
bb17b1f74c